Support declarative configuration for Java distros

[zeitlinger]

Java flavor of open-telemetry/opentelemetry-specification#4416

Currently, distributions have to implement both the old and new customizer - see #14087 (comment)

Maybe we should add a glue layer for common distro use cases, e.g. adding span processors.

TODOs:

• Expose distribution settings in AgentListener

[zeitlinger]

Grafana distro:

• after agent works without changes - because AutoConfiguredOpenTelemetrySdk.getConfig returns the config bridge: https://github.com/grafana/grafana-opentelemetry-java/blob/e01f090c6338df900b19eaa98c250b093a34fa03/custom/src/main/java/com/grafana/extensions/servertiming/ServerTimingHeaderActivator.java#L18-L22
• distribution resource: add a provider grafana_resource and and remove the default resource provider (every distro has to do it, so maybe we add a utility method somewhere)

to be continued

[zeitlinger]

@robsunday can you add your findings here?